chevron-down Created with Sketch Beta.

Carpenter v. United States: Building a Property-Based Fourth Amendment Approach to Digital Data

By Melody J. Brannon

In the United States, there are more cell phones than people. These cell phones can track our every movement, continuously and with increasing precision, even when we are not using them. That is powerful information. Until Carpenter v. United States, 138 S. Ct. 2206 (2018), was decided, the police could get this information without a warrant, and they did so frequently. In the first six months of 2018, one phone service provider reported over 32,000 requests for historical cell site location information.

Carpenter asked “how to apply the Fourth Amendment to a new phenomenon: the ability to chronicle a person’s past movements through a record of his cell phone signals.” The Court, by a 5-4 majority, held that cell site location information (CSLI), that is automatically, continuously, and comprehensively generated by a third party is protected by the Fourth Amendment. The Court recognized that we reasonably expect privacy in “the whole of our movement.” That the information is compiled by a third-party phone company “does not make it any less deserving of Fourth Amendment protection.” (Id. at 2223.)

The immediate and practical impact of Carpenter may be predictable. It intentionally staked out narrow ground, excluding, for example, real-time CLSI and data covering less than seven days. Prospectively, the government will, and probably should, routinely get a warrant, even for less comprehensive data. And Congress has proposed amended legislation to require a warrant for CSLI. Retrospectively, historical cell phone data obtained pre-Carpenter under the Stored Communications Act will likely be protected by the good faith doctrine. It will take time to understand how and when Carpenter will affect other digital information.

Carpenter’s doctrinal impact is more significant. Carpenter revealed a fractured Court, one divided between the progressive and the antediluvian. The former recognized that the Fourth Amendment must protect and accommodate rapidly advancing digital data, treading carefully so as not to “embarrass the future.” (Id. at 2220.) In doing so, the Court rejected obsolete and ill-fitting doctrines in favor of rethinking our expectation of privacy.

The dissenters insisted that this new information must bend to extant Fourth Amendment law and advocated a parsimonious property-based approach, even suggesting that we abandon the reasonable expectation of privacy model. Justice Thomas deemed the expectation-of-privacy approach to the Fourth Amendment to be a failure. Justice Gorsuch lamented the lost opportunity to consider whether digital data were protected under a Fourth Amendment positive law model. The four dissenting justices all advocated a property-based approach.

Going forward, the lesson is that we must attend to both approaches, thinking of information in terms of both property—digital “papers and effects,” to take language straight from the Amendment—and privacy in a digital world where third parties can generate “detailed, encyclopedic, and effortlessly compiled” chronicles of our lives. When we consider both approaches, the outcomes could be surprisingly consistent.

Below, we review CSLI technology, its role in the Carpenter trial, and the Stored Communications Act. Then we study the doctrinal debate over third parties, the expectation of privacy, and a property-based approach to the Fourth Amendment.

The Facts: “12,898 location points”

A string of business robberies in Ohio and Michigan led the FBI to Timothy Carpenter in 2011. An accomplice cooperating with the FBI named Carpenter and some 14 others and provided the FBI with Carpenter’s cell phone number. The prosecution then obtained court orders under the Stored Communications Act (SCA), 18 U.S.C. § 2703(d), for Carpenter’s historical CSLI. As we explain below, CSLI is a historical record of cellular connections between a phone and a cell site that identifies the phone’s approximate location at a certain time and date.

The court issued an order to Sprint to provide seven days of Carpenter’s historical CSLI. Sprint produced only two days of data, but another court order and another provider added another 127 days of CSLI. In sum, the prosecution gathered 12,898 location points cataloging Carpenter’s movements— “an average of 101 data points per day”—without a warrant. (Carpenter, 138 S. Ct. at 2212.) The geolocation information placed Carpenter’s phone, and by proxy Carpenter himself, near four of the robberies at the relevant times. (Id. at 2213.)

Carpenter moved to suppress the CSLI records. Even though the SCA statute had been followed, he argued that the warrantless search of his records violated the Fourth Amendment because he maintained a reasonable expectation of privacy in the detailed record of his physical location. The court denied his motion. (Id. at 2212.)

At trial, the government’s expert testified about CSLI, how it worked, and what Carpenter’s CSLI meant. Using the CSLI, the prosecution created “maps that placed Carpenter’s phone near four of the charged robberies.” In closing, the prosecution argued the CSLI confirmed that Carpenter was “right where the . . . robbery was at the exact time of the robbery.” (Id. at 2213.) The jury convicted Carpenter, and he was sentenced to over 100 years in prison.

On appeal, the Sixth Circuit relied on the third-party doctrine to reject Carpenter’s Fourth Amendment challenge. (United States v. Carpenter, 819 F.3d 880, 886–88 (6th Cir. 2016).) Because Carpenter voluntarily conveyed his location to the phone company by using his phone, the court held, he maintained no reasonable expectation of privacy in the records. (Id.)

The Supreme Court granted certiorari review.

The Technology: “A New Phenomenon”

Before we dive into Fourth Amendment doctrine, we should understand the technology. Cell phones generate data, frequently, automatically, and even when not in active use. Background applications run almost continuously. An unanswered incoming phone call will generate data, as will scheduled updates. When a phone is on and not in airplane mode, it is always scanning for a cellular connection. Our phones are busy even when we are not.

Whenever a phone receives or shares data, it must connect with a cell site through radio signals. Cell sites may be mounted on stationary towers or vehicles or attached to buildings or any other structure. Cell phones search for the closest and strongest site signal; when a cell site detects a radio signal from a cell phone, the site and phone connect. This is also known as a ping. As the phone moves away from one tower and toward another, the connection transfers seamlessly.

Every time a cell phone connects with a site, it records the place, time, and date of the connection, as well as the angle and strength of the signal. This is cell service location information, or CSLI. There is a line of geolocation data for every cell-to-tower contact. According to the Electronic Frontier Foundation, cell phones connect with towers on an average of every seven to nine minutes, or as frequently as every seven seconds.

And the geolocation data are increasingly precise. The more cell sites, the more exact the geolocation data. Each site may have several antennae facing different directions. Previously, a tower or site would cover a sector of several miles, meaning CSLI could only say the phone was located somewhere in that miles-wide area. That area is narrowing. In 2015, there were 118 towers and 1,086 antennas within a one-square-mile area of New York City. Today, CSLI can sometimes identify a phone’s location within feet rather than miles. And it can track with that precision “every day, every moment, over several years.” (Carpenter, 138 S. Ct. at 2220.)

This is only a brief overview to point out that CSLI is generated continuously, automatically, and with increasing comprehension. A richly sourced CSLI lesson is provided in a 2015 district court opinion, In re Application for Telephone Information Needed for a Criminal Investigation, 119 F. Supp. 3d 1011 (N.D. Cal. 2015). There, in denying a government application for CSLI, the court offered an immersion course in cell phone technology, concluding that “it has become ever more possible for the government to use CSLI to calculate a cell phone user’s location with a precision that approaches that of GPS.” (Id. at 1015.)

Existing Legislation: The Stored Communications Act

In Carpenter, the FBI obtained a court order for the CSLI under the Stored Communications Act, 18 U.S.C. § 2701 et seq. The 1986 SCA, enacted only three years after the first commercially available cell phones, regulates disclosure of information held by third-party holders of electronic communications, including CSLI. An application for Facebook data, for example, is regulated by the SCA, which requires a warrant to obtain communication content, under § 2703(a). Carpenter only implicates § 2703(d), which authorized collection of, inter alia, historical CSLI without a warrant.

A search warrant requires a magistrate to determine whether there is a fair probability that the evidence will be in the place to be searched. (See, e.g., Illinois v. Gates, 462 U.S. 213, 238 (1983).) In comparison, 18 U.S.C. § 2703(d) requires a lesser showing: “specific and articulable facts showing that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing criminal investigation.”

The traffic through this statute is immense and growing. In 2014, AT&T reported 64,703 requests for CSLI. In the first six months of 2015, Verizon received over 21,000 CSLI requests, over 100 requests per day. In the first six months of 2018, AT&T reported 32,830 historical CSLI requests.

This is not some obscure or random source for law enforcement. It is a treasure trove of historical surveillance “otherwise unknowable” to the government. (Carpenter, 138 S. Ct. at 2218.)

Pending Legislation: Senate Bill 1657

The symbiotic relationship between the judiciary and legislature is alive and well in the digital technology arena. Last term, the Court’s review in United States v. Microsoft, 138 S. Ct. 1186 (2018), was preempted by Congress. Microsoft presented the statutory (not constitutional) issue of whether the government could compel Microsoft, under the SCA, to produce electronic communications stored abroad. (Id. at 1187.) But before the Supreme Court decided the merits of the case, Congress enacted the CLOUD Act, which resolved the issue by adding a provision that required production regardless of whether it was stored within or without the United States. (CLOUD Act, Pub. L. No. 115-141, div. V, § 103(a)(1) (2018); Microsoft, 138 S. Ct. at 1188.) The United States sought a new warrant under the new statute, and the old issue before the Court was dismissed by per curium order. (Id.)

In comparison, the provision of the SCA in Carpenter also is subject to proposed legislation that would resolve the issue. Senate Bill 1657 proposes the ECPA Modernization Act of 2017, which requires a warrant for both stored content and geolocation information stored by third-party service providers. The bill, sponsored by Senators Mike Lee (R-Ut) and Patrick Leahy (D-Vt), was referred to the Senate Judiciary Committee in July of 2017. Carpenter was decided before any action was taken, but the decision won a quick and positive response from Senator Leahy, who issued a statement endorsing the Fourth Amendment’s protection of “sensitive information held by third parties,” and also advising that

. . . Congress must not rely on the courts to modernize our antiquated privacy laws. . . . My ECPA Modernization Act, which I introduced with Senator Lee, would have required a warrant for precisely the type of geolocation information at issue in Carpenter. . . . Congress must not abdicate its own responsibilities as technology advances, and it should quickly take up our legislation to accomplish these key reforms.

(Press Release, Patrick Leahy, Comment of Senator Leahy on the Supreme Court’s Decision on Cell-Site Location Information, in Carpenter v. U.S. (June 22, 2018).)

Carpenter’s Holding: Get a Warrant

Now, to the Supreme Court opinion in Carpenter. Or, actually, opinions, plural. This was a 5-4 decision, with four separate dissents.

Does the government conduct a search under the Fourth Amendment when it “accesses historical cell phone records that provide a comprehensive chronicle of the user’s past movements?” (Carpenter, 138 S. Ct. at 2211.) Carpenter’s short answer is yes because there is a reasonable expectation of privacy in the whole of our physical movements, and that expectation is not compromised just because the data are generated by a third-party phone company. The long answer, and the broader doctrinal implications, are more complicated.

Writing for the five-member majority that included Justices Ginsburg, Breyer, Sotomayor, and Kagan, Chief Justice Roberts acknowledged that property rights were the original focus of the Fourth Amendment. In Katz v. United States, 389 U.S. 347 (1967), however, the Court “expanded our conception of the Amendment to protect certain expectations of privacy as well.” (Carpenter, 138 S. Ct. at 2213.) Since then, the property-based and privacy-based rubrics have coexisted, if somewhat uneasily. In rebuffing the dissenters’ attacks on Katz, the Carpenter majority held firm—property concepts may inform the expectation of privacy, but “privacy interests do not rise or fall with property rights.” (Id. at 2214 and n.1.)

Factually, Carpenter built on Riley v. California, 134 S. Ct.2473 (2014). Riley was the Court’s technological and societal education in cell phones. There, the Court held that a warrant was required before police could search a cell phone because of the immense storage capacity of a modern cell phone. Riley recognized that cell phones are qualitatively and quantitatively different than traditional places to be searched, and that the corresponding expectation of privacy is necessarily different. They are “such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.” (Id. at 2484.)

Legally, Carpenter built on the concurrence in Jones v. United States, 565 U.S. 400, 414, 418 (2012). Jones held that the Fourth Amendment required a warrant before the government could attach a GPS to an individual’s car to monitor his travel on public streets. (Id.) The Jones majority opinion, written by Justice Scalia, resolved the question in straightforward trespassory terms. “Katz . . . established that property rights are not the sole measure of Fourth Amendment violations, but did not snuff out the previously recognized protection for property.” (Id. at 407.) The police placement of the GPS was a “classic” trespassory search that did not call for Katz analysis. (Id. at 412.)

The Jones concurrences, however, take on more significance when read in tandem with Carpenter. Five justices in Jones agreed that long-term GPS monitoring of a vehicle’s every movement usually would implicate privacy concerns. (Id. at 418, 419 (Sotomayor, Alito, Ginsburg, Breyer & Kagan, J.J., concurring).) Under either property or privacy rubrics, the long-term location monitoring in Jones was subject to the Fourth Amendment. In the Jones concurrences rests a majority that recognizes a reasonable expectation of privacy in the whole of one’s physical movements. (Id.) And that carried the day in Carpenter. (138 S. Ct. at 2217.)

CSLI triggers even greater privacy concerns than Jones’s contemporary GPS. (Id. at 2218.) As Riley noted, a cell phone tracks nearly every movement of the owner exactly, faithfully following “its owner beyond public thoroughfares into private residences, doctor’s offices, political headquarters, and potentially other revealing locales.” (Id.) And with just the click of a button, the government can access that “deep repository” of historical information with little cost. (Id.)

And unlike GPS, CSLI is historical. “The retrospective quality of the data here gives police access to a category of information otherwise unknowable.” (Id.) With GPS, the police in Jones could only track future movements after the installation. Here, the police can travel back in time to achieve “near perfect” “tireless and absolute” retrospective surveillance to reconstruct what they could not have known to look for at the time. (Id.) There is an unmistakable symmetry between the intimacy and completeness of this information and the power gained by the government in possessing this information.

Justice Kennedy’s dissent argued that CSLI was less sensitive than GPS, and therefore less entitled to protection. (Id. at 2225 (Kennedy, J., dissenting).) The forward-looking Carpenter majority had little patience for this argument, rejecting “the proposition that inference insulates a search.” (Id. at 2218 (majority opinion).) By the time the Court decided this case in 2018, the technology was seven years old. Technology advances rapidly, and the “rule the Court adopts must take account of more sophisticated systems that are already in use or in development.” (Id.)

Third-Party Doctrine: “On life support”

The government responded to the privacy expectation argument by invoking the third-party doctrine. That was a reasonable position, as it was the sole basis for the Sixth Circuit’s decision below. But the government could not make this 40-year-old doctrine relevant or meaningful in this digital age.

The third-party doctrine provides that the Fourth Amendment does not protect information voluntarily conveyed to third parties. The expectation of privacy dissipates when we convey or disclose that information to a third party, assuming the risk that they may re-disclose. And it is not just the disclosure, but the nature of the information that determines the expectation of privacy. (Id. at 2219.)

The doctrine is enshrined in two Supreme Court cases, Miller and Smith. In United States v. Miller, 425 U.S. 435 (1976), the Court held that a person depositing money at a bank had no reasonable expectation in the privacy of the bank’s transaction records. This was not because the bank “owned” the records, in terms of property rights, but that the customer “voluntarily conveyed” the information to the bank and its employees. There is no expectation of privacy in information voluntarily disclosed on the checks to a third party. (Id. at 442.)

Three years later, relying on Miller, Smith v. Maryland, 442 U.S. 735 (1979), applied this third-party reasoning to pen registers. Pen registers capture the phone numbers dialed from a landline; not any content or other information, just the number dialed. The Court found that there was no reasonable expectation of privacy in numbers dialed because all “telephone users realize that they must ‘convey’ phone numbers to the telephone company, since it is through telephone company switching equipment that their calls are completed.” (Id. at 742.) The number dialed was voluntarily conveyed to the phone company so that the call could be placed; thus, disclosure to the third party defeated any claimed expectation of privacy. (Id. at 742; Carpenter, 138 S. Ct. at 2219.)

Carpenter’s reasoning on this point is, again, built on Jones’s concurrence. Justice Sotomayor wrote,

it may be necessary to reconsider the premise that an individual has no reasonable expectation of privacy in information voluntarily disclosed to third parties. This approach is ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks.

(Jones, 565 U.S. at 417 (Sotomayor, J., concurring) (emphasis added).)

Carpenter’s majority (which included Justice Sotomayor) unhesitatingly embraced this position. These digital “detailed and comprehensive record[s] of the person’s movements” are not merely business records. (Carpenter, 138 S. Ct. at 2217.) “There is a world of difference between the limited types of personal information in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers today.” (Id. at 2219.)

The Court also caught that the government was not merely trying to apply Smith and Miller where they did not fit, but to significantly extend the third-party doctrine to a distinct category of digital information. This is not an isolated question of where someone was when he or she used a phone. “It is about a detailed chronicle of a person’s physical presence compiled every day, every moment, over several years. Such a chronicle implicates privacy concerns far beyond those considered in Smith and Miller.” (Id. at 2220.)

The Court also dismissed the other tenet of the third-party doctrine—voluntary disclosure diminishes privacy expectations. (Id.) This is a small part of the majority opinion, but one that will carry far in other contexts. Cell phones are “indispensable to participation in modern society.” (Id.) Just by carrying a phone, a trail of location data is inevitably created by the third party, with no active participation by the owner. “In no meaningful sense” has the phone’s owner “voluntarily assumed the risk of turning over a comprehensive dossier of his physical movements.” (Id.)

The majority’s easy turn away from the third-party doctrine was not just a rebuke of the government but revealed the Court’s division. Justice Kennedy’s dissent, joined by Justices Thomas and Alito, was a staunch defense of the 40-year-old doctrine. (Id. at 2223–25.) The records were generated and belonged to the phone company. His dissent resolutely refuses any distinction between CSLI and 1970s era bank records and insists this factor defeats any Fourth Amendment claim. (Id. at 2225, 2227.)

On this point, Justice Gorsuch’s dissent is remarkable. He comes out of the gate against the third-party doctrine: “In the years since its adoption, countless scholars, too, have come to conclude that the third-party doctrine is not only wrong, but horribly wrong. . . . The reasons are obvious.” (Id. at 2262 (quoting Orin Kerr, The Case for the Third-Party Doctrine, 107 Mich. L. Rev. 561 (2009)) (internal marking omitted).) The Court has never, per Justice Gorsuch, persuasively justified the doctrine. The voluntary disclosure theory is questionable: “Consenting to give a third-party access to private papers that remain my property is not the same thing as consenting to a search of those papers by the government.” (Id. at 2263 (emphasis in original).)

If the majority did not end the third-party doctrine, Justice Gorsuch may have landed the fatal blow: “In the end, what do Smith and Miller add up to? A doubtful application of Katz that lets the government search almost whatever it wants whenever it wants.” (Id. at 2264.)

The Court did not overrule the doctrine. Nor was it asked to. As Justice Gorsuch observed, “Smith and Miller aren’t quite left for dead; they just no longer have the clear reach they once did.” (Id. at 2267.) But there is little life left in Smith and Miller in our digital information age. If not expressly overruled, they will surely die of old age after this six-justice eulogy.

“Our decision today is a narrow one.”

Building on Riley and Jones, Carpenter recognized an expectation of privacy in this new phenomenon of comprehensive digital location information, and outrightly rejected the government’s third-party doctrine arguments.

But the Court was still cautious, calling its decision narrow. (Id. at 2220.) It did not contemplate real-time CSLI, tower dumps, or other business records that might reveal location. Nor did it question traditional surveillance techniques or national security or foreign affairs information collection. “[T]he Court must tread carefully . . . to ensure we do not embarrass the future.” (Id.)

Like any warrant requirement, there are certain to be exigency and emergency exceptions. (Id. at 2222–23.) And the Court imposed another arbitrary limitation that no doubt will invite more litigation rather than guide the stakeholders: “It is sufficient for our purposes today to hold that accessing seven days of CSLI constitutes a Fourth Amendment search.” (Id. at 2217 and n.3; see id. at 2267 (Gorsuch, J., dissenting) (“Why seven days instead of ten or three or one?”).)

The majority’s limitations did little to assuage the dissenters, who expressed a somewhat feverish concern about hobbling law enforcement. This conceit ignores the ease with which law enforcement can obtain a warrant. CSLI is not off limits. The SCA mirrors a warrant’s procedure, as both require written application and judicial authorization. The difference is that the statute requires specific facts “relevant and material to an ongoing investigation” while a warrant requires probable cause. And, on the ground, the daylight between those two standards often is faint.

The Dissenters: A Property-Based Approach to the Fourth Amendment

The majority decision rests, doctrinally, on Katz’s reasonable expectation of privacy and rejects the third-party doctrine. If there is a unifying doctrinal theme of the dissenters, it is that the property-based approach to the Fourth Amendment has been ignored, if not abandoned. The actual wording of the Fourth Amendment protects the right to be secure “in their persons, houses, papers, and effects,” saying nothing, as Justice Thomas notes, about a reasonable expectation of privacy. (Id. at 2235–36 (Thomas, J., dissenting).) Justice Kennedy’s defense of Smith and Miller was staked in a property-based rubric. “The Court unhinges Fourth Amendment doctrine from the property-based concepts that have long grounded the analytic framework that pertains in [Smith and Miller].” (Id. at 2224 (Kennedy, J., dissenting).) But even Justice Kennedy’s dissent allowed that “Miller and Smith may not apply when the Government obtains the modern-day equivalents of an individual’s own ‘papers’ or ‘effects,’ even when those papers or effects are held by a third party.” (Id. at 2230 (emphasis added).) The case should have been resolved based on “interpreting accepted property principles as the baseline for reasonable expectations of privacy.” (Id. at 2235.) Justice Thomas, however, would have gone much further.

Justice Thomas’s dislike of Katz

Justice Thomas believes that Katz’s reasonable expectation of privacy approach should be abandoned because it has no basis in the text or history of the Fourth Amendment. (Id. at 2236 (Thomas, J., dissenting).) “The word ‘privacy’ does not appear in the Fourth Amendment (or anywhere else in the Constitution for that matter).” (Id. at 2239.) The Fourth Amendment protects against unreasonable searches of “their persons, houses, papers, and effects.” (Id. at 2235.) Justice Thomas would conclude that the CSLI was the property of the phone company, not Carpenter’s property, and therefore not subject to the Fourth Amendment. Property, not privacy, is the only acceptable constitutional inquiry.

But a property-based argument was not squarely before the Court—it was not a primary, or even secondary, argument from Carpenter at any stage of the proceedings or the court below, as the government noted in its response. (Brief of Respondent United States at 41, Carpenter v. United States, 138 S. Ct. 2206 (2018) (No. 16-402).) It was not fully briefed, argued, or presented, as Justice Thomas noted. (Carpenter, 138 S. Ct. at 2242 (Thomas, J., dissenting).) Justice Thomas was debating an all-but-absent issue. (Id.)

This echoed his frustration in Byrd v. United States, 138 S. Ct. 1518 (2018), another Fourth Amendment case decided in the same term. There, the Court considered whether Byrd had a reasonable expectation of privacy in the rental car he was driving with the permission of the renter, even though his name was not on the rental agreement as an authorized driver. Justice Thomas, joined by Justice Gorsuch, concurred in the result, noting his doubts about Katz, but framing the question as one of property: whether the rental car was “his effect.” Justice Thomas was eager to speak to the concept, but the property-based approach was “glossed over.” “In an appropriate case, I would welcome briefing and argument on these questions.” (Id. at 1531 (Thomas, J., concurring).)

With more factual development, there is a solid argument that digital CSLI records are, in fact, the “papers and effects” of the user. Justice Thomas did not allow that more than one person or entity can hold rights in the same property, but there is a digital case to be made on this point, as Justice Gorsuch later admitted. (Carpenter, 138 S. Ct. at 2270 (Gorsuch, J., dissenting).) Justice Thomas introduced the bundle of rights that attend property ownership—“he does not maintain them, he cannot control them, and he cannot destroy them.” (Id. at 2235 (Kennedy, J., joined by Thomas & Alito, JJ., dissenting). See Loretto v. Teleprompter Manhattan CATV Corp., 458 U.S. 419, 436 (1983) (describing the bundle of property rights, including the power to exclude, use, loan, and possess).) The bundle of property rights that attend to physical property also can attend to digital data, including the right to use, to bailment, and to exclude. (See Carpenter, 138 S. Ct. at 2268–69 (Gorsuch, J., dissenting) (contemplating bailment).) The concept that digital data such as CSLI is “papers, and effects” and therefore protected under a property-based rubric, has not yet been fully considered by the Court. The argument must be made, and Justice Thomas invites it.

Despite Justice Thomas’s thorough historical and legal criticism, Katz was not on the chopping block. The value of Justice Thomas’s Katz attack is, in part, that we should advance both property-based and privacy-based arguments, even on the heels of Carpenter.

Next up: Justice Alito, Joined by Justice Thomas, Dissents

Justice Alito’s full-throated dissent was joined only by Justice Thomas. Justice Alito said that allowing a defendant to object to a third party’s property, as he read the majority opinion, is “revolutionary” and “destabilizes long-established Fourth Amendment doctrine.” (Id. at 2247 (Alito, J., dissenting).)

Much ink was spilled on comparing warrants, orders, and subpoenas, which we will not address here. Justice Alito keyed in on the property argument. The records were created and possessed by the phone company. In contrast, “Carpenter, in short, has no meaningful control over the cell-site records, which are created, maintained, altered, used, and eventually destroyed by his cell service providers.” (Id. at 2257.) This, too, is the language of the bundle of property rights. Without a vested property interest in the CSLI, Carpenter had no call for Fourth Amendment protection. And Justice Alito was quick to dismiss any argument that the Telecommunications Act granted him a property interest, which we discuss below in context of the positive law model. For Justice Alito’s purposes, the statutory interest was too tenuous. In all, “there is no plausible ground for maintaining that the information at issue here represents Carpenter’s ‘papers’ or ‘effects.’” (Id. at 2259.)

Justice Gorsuch and the Positive Law Model

If Justice Gorsuch was not a fan of Smith and Miller, he was no cheerleader for Katz, either. “Katz’s problems start with the text and original understanding of the Fourth Amendment, as Justice Thomas thoughtfully explains today. . . . The Amendment’s protections do not depend on the breach of some abstract ‘expectation of privacy’ whose contours are left to the judicial imagination. Much more concretely, it protects your ‘person,’ and your ‘houses, papers, and effects.’” (Id. at 2264 (Gorsuch, J., dissenting).) Like the third-party doctrine, Katz has never been “sufficiently justified.” (Id. at 2265.) Unlike Justice Thomas, however, Justice Gorsuch allowed Katz to survive as “one way to prove a Fourth Amendment interest.” (Id. at 2272.)

Justice Gorsuch offered “another way.” Ask “if a house, paper or effect was yours under the law.” (Id. at 2268.) “What kind of legal interest is sufficient to make something yours? And what source of law determines that?” (Id.) The answer is to be found, perhaps, in the positive law model. (Id.)

The positive law model of the Fourth Amendment looks at “whether there is some law that prohibits or restricts the government’s actions (other than the Fourth Amendment itself.)” It asks whether the government broke the law to obtain the information, or whether the information was legally available to the public. (Orin Kerr, Four Models of Fourth Amendment Protection, 60 Stan. L. Rev. 503, 516 (2007); William Baude & James Y. Stern, The Positive Law Model of the Fourth Amendment, 129 Harv. L. Rev. 1821, 1825 (2016).) The positive law model may consider possessory interest, trade secret law, or even FAA regulations of airspace. (Kerr, Four Models, at 517.)

For example, the federal Telecommunications Act, 47 U.S.C. § 222(c), bars phone companies from disclosing CSLI to the public. (Carpenter, 138 S. Ct. at 2242 (Thomas, J., dissenting).) The phone company holds the information, but the phone customer has a proprietary interest in the information. “Those interests might even rise to the level of a property right,” per Justice Gorsuch. (Id. at 2272 (Gorsuch, J., dissenting). It was not enough to convince Justice Kennedy or Justice Alito. (Id. at 2242 (Kennedy, J., dissenting), 2258 (Alito, J., dissenting) (“the Telecommunications Act is insufficient because it does not give Carpenter a property right in the cell-site records”).) But if it did, the positive law model could inform that Carpenter was entitled to the protection of the Fourth Amendment under a property-based approach. (Kerr, Four Models, at 516.) But because this approach was not before the Court, we do not know the answer.

Justice Gorsuch admitted, “I do not begin to claim all the answers today, but (unlike with Katz) at least I have a pretty good idea what the questions are.” (Id. at 2268 (Gorsuch, J., dissenting).) Those ideas are, predictably, property-based. “The fact that a third party has access to or possession of your papers and effects does not necessarily eliminate your interest in them.” (Id.) He offered a theory of bailment applied to digital data, and even a theory of involuntary bailment in the way we must store data with third parties. (Id.)

Whether looking to a general property-based approach or a more specific positive law model, the modern-day relationship between Carpenter and his phone company, Sprint, deserves attention. Justice Gorsuch and Justice Kennedy both considered bailment and how it fits into a property-based approach. (Id. at 2268–69 (Gorsuch, J., dissenting) & 2230 (Kennedy, J., dissenting).) To borrow from “ancient principle,” as Justice Gorsuch does (id. at 2269), compare Ward v. Macauley, 100 Eng. Rep. 1135, 1135 (K.B. 1791),

To entitle a man to bring trespass, he must at the time when the act was done, which constitutes the trespass, either have the actual possession of the thing, which is the object of the trespass, or else he must have the constructive possession in respect of the right being actually vested in him. The right to personal property is not divested out of the owner, because he gives the temporary use of it to another. In the case of a carrier, the owner may maintain trespass, on the ground of his having the general property; and the carrier trover on account of his special property.

(Id. (emphasis added).) Furthermore, from Chief Justice Kenyon: “In the case put of a carrier, there is a mixed possession: actual possession in the carrier, and an implied possession in the owner.” (Id. (emphasis added).) And Justice Buller: “The carrier is considered in law as the servant of the owner, and the possession of the servant is the possession of the master.” (Id. (emphasis added).) The dissenters were steeped in lessons of legal history. (See, e.g., Carpenter, 138 S. Ct. at 2239–40 (Thomas, J., dissenting).) Here, we have a 1791 case considering carriers. Sprint, too, is a carrier, and Carpenter the owner, or so the argument could be made.

Consistent with Ward’s principle, Justice Gorsuch “doubt[s] complete ownership or exclusive control of property is always a necessary condition to the assertion of a Fourth Amendment right.” (Id. at 2269 (Gorsuch, J., dissenting).) And just because “you have to entrust a third party with your data”—this would seem to be the case with CSLI—“doesn’t necessarily mean you should lose all Fourth Amendment protections in it.” (Id. at 2270.) These questions suggest that, in his view, CSLI may qualify as Carpenter’s “papers, and effects.” But he does not confirm, only intimates, because, as in Byrd, the arguments were not presented:

Unfortunately, too, this case marks the second time this Term that individuals have forfeited Fourth Amendment arguments based on positive law by failing to preserve them. See Byrd, . . . Litigants have had fair notice since at least United States v. Jones (2012) and Florida v. Jardine’s (2013) that arguments like these may vindicate Fourth Amendment interests even where Katz arguments do not. Yet the arguments have gone unmade, leaving courts to the usual Katz handwaving. These omissions do not serve the development of a sound or fully protective Fourth Amendment jurisprudence.

(Id. at 2272.)

Litigators know all too well that we make strategic decisions about what issues and arguments to pursue, and those to let rest. We also know all too well that judges are not always wise to those decisions. Both Carpenter and Byrd won, and, from a defense perspective, deservedly so. Whether or why the parties pursued certain theories or not is left with them, and nothing here should suggest any criticism, only praise for defending the Fourth Amendment. But from now on, we should give serious thought to property-based arguments.

Going Forward

Some thoughts going forward: Consider both privacy and property-based approaches, whether challenging or defending searches. Think through the positive-law model. But remember that Katz is still the law. The trilogy of Carpenter, Riley, and the Jones concurrence signal an expansive view of privacy in the digital age. This should apply to all sorts of other digital-age information—geotagging in social media, running apps, maps, Find My iPhone, GPS tracking used by Absolute Software’s LoJack, media access control (MAC)—it is a long and rapidly growing list. And so too grows our reliance on smartphones. Pew Research Center reports that “one-in-five American adults are ‘smartphone-only’ internet users—meaning they own a smartphone, but do not have a traditional home broadband device.” (Mobile Fact Sheet, Pew Research Ctr. (Feb. 5, 2018).)

The third-party doctrine is, as Justice Gorsuch noted, on life support. The plug only need be pulled. A direct challenge may have traction, and singular reliance to save a search may be risky.

Seven days was a marker in Carpenter, but only because those were the facts before the Court. Data can be quantified in different ways. Days can mark time, but data points produced in that time could range from insignificant to thousands. Remember, phones can check in with towers as often as every seven seconds. Pull information from nonlegal sources, as the Carpenter Court did. And watch for legislation amending the SCA.

Also consider when a search of digital data occurs. The search of a house is easy. Enter the house, search the room, seize the contraband, and leave. Digital searches are much different. (Professor Orin Kerr considers some questions at When Does a Carpenter Search Start—And When Does It Stop?, Volokh Conspiracy (July 6, 2018 3:34 PM).)

Remember, there is more than one way the government can access location information. Follow the path. Did the government try to use a “private actor”? If so, that private actor actually may be a government agent. (See United States v. Ackerman, 831 F.3d 1292, 1308 (10th Cir. 2016) (finding the private agency NCMEC was a government agent when its employee opened Mr. Ackerman’s emails and attachments).)

Even as the theoretical precision of CSLI increases, the trustworthiness of the technology is vulnerable to attack. That CSLI is robust and voluminous does not mean that it is accurate or reliable. (Carpenter, 138 S. Ct. at 2225 (Kennedy, J., dissenting) (discussing the imprecision of CSLI: “In rural areas cell-site records can be up to 40 times more imprecise.”).)


Whether challenging or defending searches, we should pay thoughtful attention to the doctrinal issues in Carpenter. As our understanding of digital information advances, old ideas about physical property and possession must recede, or at least make room. Digital data can be “papers, and effects” protected by the Fourth Amendment, and that concept is strengthened with the demise of the anachronistic third-party doctrine. We could be surprised at the vitality of a positive law model.

The Court has invited these debates. Now we need to make the arguments.

Resources and Reading

Susan Freiwald, Cell Phone Location Data and the Fourth Amendment: A Question of Law, Not Fact, 70 Md. L. Rev. 681 (2011).

Louis Matsakis, The Supreme Court Just Greatly Strengthened Digital Privacy, Wired, June 22, 2018.

Brief of Amici Curiae Electronic Frontier Foundation, et al., Carpenter v. United States, 138 S. Ct. 2206 (2018) (No. 16-402) (filed August 14, 2017), available at SCOTUSBlog.

For cell site statistics, see or The Statistics Portal,

Mobile Fact Sheet, Pew Research Ctr. (Feb. 5, 2018).

AT&T, AT&T Transparency Report (Feb. 12, 2018).

Rodolfo Ramirez, Kelly King & Lori Ring, Location! Location! Location!: Data Technologies and the Fourth Amendment, 30 ABA Criminal Justice, no. 4, Winter 2016, at 20.

ECPA Modernization Act of 2017, S.B. 1657.

Robinson Meyer, Do Police Need a Warrant to See Where a Phone Is?, The Atl., Aug. 8, 2015.

V. Alexander Monteith, Cell Site Location Information: A Catalyst for Change in Fourth Amendment Jurisprudence, 27 Kan. J.L. & Pub. Pol’y 82 (Fall 2017).

Olivia Castillo, Is Privacy Still Possible? The Fourth Amendment in an Age of (Digital) Surveillance, 33 ABA Criminal Justice, no. 1, Spring 2018, at 8.

Melody J. Brannon is the federal public defender for the District of Kansas.

The material in all ABA publications is copyrighted and may be reprinted by permission only. Request reprint permission here.